Regulation of MHC class II expression in glioma cells by class II transactivator (CIITA)

Non-Immune-Mediated, p27-Associated, Growth Inhibition of Glioblastoma by Class-II-Transactivator (CIITA)

BACKGROUND

Previous works have shown that the expression of Class-II-Transactivator (CIITA) in tumor cells reduces the growth of glioblastoma (GB) in animal models, but immune effects cannot solely explain this. Here, we searched for immune-independent effects of CIITA on the proliferation of GB.

METHODS

Murine GL261 and human U87, GM2 and GM3 malignant glioma cells were transfected with CIITA. NSG (immunodeficient) and nude (athymic) mice were injected in the striatum with GL261-wildtype (-WT) and -CIITA, and tumor growth was assessed by immunohistology and luminescence reporter genes. Clonogenic, sphere-formation, and 3D Matrigel-based in vitro growth assays were performed to compare the growth of WT versus CIITA-expressing murine and human cells. Bulk RNA sequencing and RT2 qRT-PCR profiler arrays were performed on these four cell lines to assess RNA expression changes following CIITA transfection. Western blot analysis on several proliferation-associated proteins was performed.

RESULTS

The intracerebral growth of murine GL261-CIITA cells was drastically reduced both in immunodeficient and athymic mice. Tumor growth was reduced in vitro in three of the four cell types. RNA sequencing and RT2 profiler array experiments revealed a modulation of gene expression in the PI3-Akt, MAPK- and cell-cycle regulation pathways following CIITA overexpression. Western blot analysis showed an upregulation of p27 in the growth-inhibited cells following this treatment. PDGFR-beta was downregulated in all cells. We did not find consistent regulation of other proteins involved in GB proliferation.

CONCLUSIONS

Proliferation is drastically reduced by CIITA in GB, both in vivo and in vitro, notably in association with p27-mediated inhibition of cell-cycle pathways.

Limited Effects of Class II Transactivator-Based Immunotherapy in Murine and Human Glioblastoma

BACKGROUND

The major histocompatibility complex type II is downregulated in glioblastoma (GB) due to the silencing of the major transcriptional regulator class II transactivator (CIITA). We investigated the pro-immunogenic potential of CIITA overexpression in mouse and human GB.

METHODS

The intracerebral growth of wildtype GL261-WT cells was assessed following contralateral injection of GL261-CIITA cells or flank injections with GL261-WT or GL261-CIITA cells. Splenocytes obtained from mice implanted intracerebrally with GL261-WT, GL261-CIITA cells or phosphate buffered saline (PBS) were transferred to other mice and subsequently implanted intracerebrally with GL261-WT. Human GB cells and (syngeneic) GB-infiltrating immune cells were isolated from surgical samples and co-cultured with GB cells expressing CIITA or not, followed by RT-qPCR assessment of the expression of key immune regulators.

RESULTS

Intracerebral vaccination of GL261-CIITA significantly reduced the subsequent growth of GL261-WT cells implanted contralaterally. Vaccination with GL261-WT or -CIITA subcutaneously, however, equivalently retarded the intracerebral growth of GL261 cells. Adoptive cell transfer experiments showed a similar antitumor potential of lymphocytes harvested from mice implanted intracerebrally with GL261-WT or -CIITA. Human GB-infiltrating myeloid cells and lymphocytes were not activated when cultured with CIITA-expressing GB cells. Tumor-infiltrating NK cells remained mostly inactivated when in co-culture with GB cells, regardless of CIITA.

CONCLUSION

these results question the therapeutic potential of CIITA-mediated immunotherapy in glioblastoma.

Cytotoxic CD4+ T cells in chronic viral infections and cancer

CD4+ T cells play an important role in immune responses against pathogens and cancer cells. Although their main task is to provide help to other effector immune cells, a growing number of infections and cancer entities have been described in which CD4+ T cells exhibit direct effector functions against infected or transformed cells. The most important cell type in this context are cytotoxic CD4+ T cells (CD4+ CTL). In infectious diseases anti-viral CD4+ CTL are mainly found in chronic viral infections. Here, they often compensate for incomplete or exhausted CD8+ CTL responses. The induction of CD4+ CTL is counter-regulated by Tregs, most likely because they can be dangerous inducers of immunopathology. In viral infections, CD4+ CTL often kill via the Fas/FasL pathway, but they can also facilitate the exocytosis pathway of killing. Thus, they are very important effectors to keep persistent virus in check and guarantee host survival. In contrast to viral infections CD4+ CTL attracted attention as direct anti-tumor effectors in solid cancers only recently. Anti-tumor CD4+ CTL are defined by the expression of cytolytic markers and have been detected within the lymphocyte infiltrates of different human cancers. They kill tumor cells in an antigen-specific MHC class II-restricted manner not only by cytolysis but also by release of IFNγ. Thus, CD4+ CTL are interesting tools for cure approaches in chronic viral infections and cancer, but their potential to induce immunopathology has to be carefully taken into consideration.

Human dendritic cell subsets in the glioblastoma-associated microenvironment

Glioblastoma (GBM) is the most aggressive type of glioma (Grade IV). The presence of cytotoxic T lymphocyte (CTLs) has been associated with improved outcomes in patients with GBM, and it is believed that the activation of CTLs by dendritic cells may play a critical role in controlling the growth of GBM. DCs are professional antigen-presenting cells (APC) that orchestrate innate and adaptive anti-GBM immunity. DCs can subsequently differentiate into plasmacytoid DCs (pDC), conventional DC1 (cDC1), conventional (cDC2), and monocyte-derived DCs (moDC) depending on environmental exposure. The different subsets of DCs exhibit varying functional capabilities in antigen presentation and T cell activation in producing an antitumor response. In this review, we focus on recent studies describing the phenotypic and functional characteristics of DC subsets in humans and their respective antitumor immunity and immunotolerance roles in the GBM-associated microenvironment. The critical components of crosstalk between DC subsets that contribute significantly to GBM-specific immune responses are also highlighted in this review with reference to the latest literature. Since DCs could be prime targets for therapeutic intervention, it is worth summarizing the relevance of DC subsets with respect to GBM-associated immunologic tolerance and their therapeutic potential.

H3G34-Mutant Gliomas-A Review of Molecular Pathogenesis and Therapeutic Options

The 2021 World Health Organization Classification of Tumors of the Central Nervous System reflected advances in understanding of the roles of oncohistones in gliomagenesis with the introduction of the H3.3-G34R/V mutant glioma to the already recognized H3-K27M altered glioma, which represent the diagnoses of pediatric-type diffuse hemispheric glioma and diffuse midline glioma, respectively. Despite advances in research regarding these disease entities, the prognosis remains poor. While many studies and clinical trials focus on H3-K27M-altered-glioma patients, those with H3.3-G34R/V mutant gliomas represent a particularly understudied population. Thus, we sought to review the current knowledge regarding the molecular mechanisms underpinning the gliomagenesis of H3.3-G34R/V mutant gliomas and the diagnosis, treatment, long-term outcomes, and possible future therapeutics.

Updates in Glioblastoma Immunotherapy: An Overview of the Current Clinical and Translational Scenario

Glioblastoma (GBM) is the most common and aggressive central nervous system tumor, requiring multimodal management. Due to its malignant behavior and infiltrative growth pattern, GBM is one of the most difficult tumors to treat and gross total resection is still considered to be the first crucial step. The deep understanding of GBM microenvironment and the possibility of manipulating the patient's innate and adaptive immune system to fight the neoplasm represent the base of immunotherapeutic strategies that currently express the future for the fight against GBM. Despite the immunotherapeutic approach having been successfully adopted in several solid and haematologic neoplasms, immune resistance and the immunosuppressive environment make the use of these strategies challenging in GBM treatment. We describe the most recent updates regarding new therapeutic strategies that target the immune system, immune checkpoint inhibitors, chimeric antigen receptor T cell therapy, peptide and oncolytic vaccines, and the relevant mechanism of immune resistance. However, no significant results have yet been obtained in studies targeting single molecules/pathways. The future direction of GBM therapy will include a combined approach that, in contrast to the inescapable current treatment modality of maximal resection followed by chemo- and radiotherapy, may combine a multifaceted immunotherapy treatment with the dual goals of directly killing tumor cells and activating the innate and adaptive immune response.

PD-L2 expression is correlated with the molecular and clinical features of glioma, and acts as an unfavorable prognostic factor

Background: Gliomas are aggressive tumors with various molecular and clinical characteristics and exhibit strongly resistance to radio-chemotherapy. Programmed cell death 1 ligand 2 (PD-L2) is a cell surface protein, which was reported in many cancers, modulating cancer-associated immune responses, while the role of PD-L2 in gliomas remained unclear. Herein, we aimed to investigate the biological behaviors and clinical prognostic values of PD-L2 in gliomas.

Methods: Totally, we enrolled RNA sequencing data of 325 glioma samples from Chinese Glioma Genome Atlas (CGGA) as training cohort and RNA expression data of 1032 samples from The Cancer Genome Atlas (TCGA) dataset as validation cohort in this research. Then, the clinical and molecular characteristics, and the prognostic value of PD-L2 were analyzed.

Results: We found that PD-L2 expression level was significantly upregulated in higher grade glioma and IDH wild-type glioma. Receiver Operating Characteristic (ROC) analysis revealed that PD-L2 was a potential indicator of mesenchymal subtype. PD-L2 exhibited tight relationship with immune response and immune-modulating process in glioma. Moreover, PD-L2 expression level could predict unfavorable prognoses of patients independent of age, grade, IDH status and 1p/19q status.

Conclusions: Our study revealed that PD-L2 was closely related with inflammation and immune response. Patients with lower PD-L2 expression level tended to experience improved survival. Targeting PD-L2 may become a valuable approach for the treatment of gliomas in clinical practice.

Plasmacytoid dendritic cell in immunity and cancer

Plasmacytoid dendritic cells (pDCs) comprise a subset of dendritic cells characterized by their ability to produce large amount of type I interferon (IFN-I/α). Originally recognized for their role in modulating immune responses to viral stimulation, growing interest has been directed toward their contribution to tumorigenesis. Under normal conditions, Toll-like receptor (TLR)-activated pDCs exhibit robust IFN-α production and promote both innate and adaptive immune responses. In cancer, however, pDCs demonstrate an impaired response to TLR7/9 activation, decreased or absent IFN-α production and contribute to the establishment of an immunosuppressive tumor microenvironment. In addition to IFN-α production, pDCs can also act as antigen presenting cells (APCs) and regulate immune responses to various antigens. The significant role played by pDCs in regulating both the innate and adaptive components of the immune system makes them a critical player in cancer immunology. In this review, we discuss the development and function of pDCs as well as their role in innate and adaptive immunity. Finally, we summarize pDC contribution to cancer pathogenesis, with a special focus on primary malignant brain tumor, their significance in the era of immunotherapy and suggest potential strategies for pDC-targeted therapy.

Regulatory landscape and clinical implication of MBD3 in human malignant glioma

In this article we inspect the roles and functions of the methyl-CpG-binding domain protein 3 (MBD3) in human malignant glioma, to assess its potential as an epigenetic biomarker for prognosis. The regulatory effects of MBD3 on glioma transcriptome were first profiled by high-throughput microarray. Our results indicate that MBD3 is involved in both transcriptional activation and repression. Furthermore, MBD3 fine-controls a spectrum of proteins critical for cellular metabolism and proliferation, thereby contributing to an exquisite anti-glioma network. Specifically, the expression of MHC class II molecules was found to positively correlate with MBD3, which provides new insight into the immune escape of gliomagenesis. In addition, MBD3 participates in constraining a number of oncogenic non-coding RNAs whose over-activation could drive cells into excessive growth and higher malignancy. Having followed up a pilot cohort, we noted that the survival of malignant glioma patients was proportional to the content of MBD3 and 5-hydroxymethylcytosine (5hmC) in their tumor cells. The progression-free survival (PFS) and overall survival (OS) were relatively poor for patients with lower amount of MBD3 and 5hmC in the tissue biopsies. Taken together, this work enriches our understanding of the mechanistic involvement of MBD3 in malignant glioma.

Epigenetic Changes of the Immune System with Role in Tumor Development

Tumor development is closely related to chronic inflammation and to evasion of immune defense mechanisms by neoplastic cells. The mediators of the inflammatory process as well as proteins involved in immune response or immune response evasion can be subject to various epigenetic changes such as methylation, acetylation, or phosphorylation. Some of these, such as cytokine suppressors, are undergoing repression through epigenetic changes, and others such as cytokines or chemokines are undergoing activation through epigenetic changes, both modifications having as a result tumor progression. The activating changes can affect the receptor molecules involved in immune response and these promote inflammation and subsequently tumor development while the inactivating changes seem to be related to the tumor regression process. The proteins involved in antigen presentation, and, therefore in immune response escape, such as classical HLA proteins and related APM (antigen presentation machinery) with their epigenetic changes contribute to the tumor development process, either to tumor progression or regression, depending on the immune effector cells that are in play.

Peptide vaccines for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is an extremely malignant brain tumor for which current therapies do little to remedy. Despite aggressive treatment with surgery, radiation therapy, and chemotherapy, tumors inevitably recur as a direct consequence of the infiltrative nature of GBM. The poor prognosis of patients with GBM underscores the clear and urgent need for more precise and potent therapies. Immunotherapy is emerging as a promising means to treat GBM based on the immune system's capacity to mediate tumor-specific cytotoxicity. In this review, we will discuss the use of peptide vaccines for the treatment of GBM. The simplicity of peptide vaccines and their ability to elicit tumor antigen-specific immune responses make them an invaluable tool for the study of brain tumor immunotherapy.

Proximity ligation assay evaluates IDH1R132H presentation in gliomas

For a targeted cancer vaccine to be effective, the antigen of interest needs to be naturally processed and presented on MHC by the target cell or an antigen-presenting cell (APC) in the tumor stroma. The presence of these characteristics is often assumed based on animal models, evaluation of antigen-overexpressing APCs in vitro, or assays of material-consuming immune precipitation from fresh solid tissue. Here, we evaluated the use of an alternative approach that uses the proximity ligation assay (PLA) to identify the presentation of an MHC class II-restricted antigen in paraffin-embedded tissue sections from patients with brain tumors. This approach required a specific antibody directed against the epitope that was presented. We used an antibody that specifically binds an epitope of mutated isocitrate dehydrogenase type 1 (IDH1R132H), which is frequently expressed in gliomas and other types of tumors. In situ PLA showed that the IDH1R132H epitope colocalizes with MHC class II in IDH1R132H-mutated glioma tissue. Moreover, PLA demonstrated colocalization between the class II epitope-containing melanoma antigen New York esophageal 1 and MHC class II. Collectively, our data suggest that PLA may be a useful tool to acquire information on whether an antigen is presented in situ, and this technique has potential to guide clinical studies that use antigen-specific cancer immunotherapy.

IFNγ in combination with IL-7 enhances immunotherapy in two rat glioma models

Peripheral immunization, using a combination of interferon-gamma (IFNγ)- and interleukin-7 (IL-7)-producing tumor cells, eradicated 75% of pre-established intracerebral N32 rat glioma tumors, and prolonged survival in the more aggressive RG2 model. Rats immunized with IFNγ- and IL7-transduced N32 cells displayed increases in IFNγ plasma levels and proliferating circulating T cells when compared with rats immunized with N32-wild type cells. Following irradiation, the expression of MHC I and II was high on N32-IFNγ cells, but low on RG2-IFNγ cells. In conclusion, IFNγ and IL-7 immunizations prolong survival in two rat glioma models.

Contrasting effects of IFNα on MHC class II expression in professional vs. nonprofessional APCs: Role of CIITA type IV promoter

We previously demonstrated that, in ex vivo cultures, IFNα downregulates the expression of MHC class II (MHCII) genes in human non-professional APCs associated with pancreatic islets. IFNα has an opposing effect on MHCII expression in professional APCs. In this study, we found that the mechanism responsible for the IFNα-mediated MHCII's downregulation in human MHCII-positive non-professional antigen presenting human non-hematopoietic cell lines is the result of the negative feedback system that regulates cytokine signal transduction, which eventually inhibits promoters III and IV of CIITA gene. Because the CIITA-PIV isoform is mostly responsible for the constitutive expression of MHCII genes in non-professional APCs, we pursued and achieved the specific knockdown of CIITA-PIV mRNA in our in vitro system, obtaining a partial silencing of MHCII molecules similar to that obtained by IFNα. We believe that our results offer a new understanding of the potential significance of CIITA-PIV as a therapeutic target for interventional strategies that can manage autoimmune disease and allograft rejection with little interference on the function of professional APCs of the immune system.

Multi-walled carbon nanotube (MWCNT) synthesis, preparation, labeling, and functionalization

Nanomedicine is a growing field with a great potential for introducing new generation of targeted and personalized drug. Amongst new generation of nano-vectors are carbon nanotubes (CNTs), which can be produced as single or multi-walled. Multi-walled carbon nanotubes (MWCNTs) can be fabricated as biocompatible nanostructures (cylindrical bulky tubes). These structures are currently under investigation for their application in nanomedicine as viable and safe nanovectors for gene and drug delivery. In this chapter, we will provide you with the necessary information to understand the synthesis of MWCNTs, functionalization, PKH26 labeling, RNAi, and DNA loading for in vitro experimentation and in vivo implantation of labeled MWCNT in mice as well as materials used in this experimentation. We used this technique to manipulate microglia as part of a novel application for the brain cancer immunotherapy. Our published data show this is a promising technique for labeling, and gene and drug delivery into microglia.

Molecular pathological approaches to human tumor immunology

Research on human tumor immunology has greatly advanced in the past two decades. Many immunogenic tumor antigens have been identified, and some of these antigens entered in clinical trials. Consequently, it has been shown that these antigens can inhibit tumor growth in patients to some extent, indicating that they act as potent immunogenic therapeutic vaccines in cancer patients with malignancies originating from various tissues. These patients had antigen-specific cytotoxic T-lymphocyte (CTL) responses when assessed on tetramer, enzyme-linked immunospot (ELISPOT), T-cell clonotype and CTL induction efficiency. Thus, it has become clear that human tumor vaccines can evoke clinical and immunological anti-tumor responses in patients. The tumor regression effects of tumor vaccines, however, are generally low, and it is obvious that current vaccination protocols are generally too weak to provide substantial and satisfactory clinical benefits. This means that other drastic and more potent clinical and immunological protocols are required in cancer immunotherapy. To find such efficient protocols the basic immunological and biological properties of cancers must be investigated. In the present review the identification of human tumor antigens recognized on CTL and the clinical trials are introduced. Next, the most recent analysis of human cancer-initiating cell (cancer stem cell)-associated antigens is described. These antigens might be able to act as 'universal, general and fundamental' tumor antigens. Also present is the authors' recent study for increasing cross-presentation efficiency in dendritic cells and subsequent enhancement of human leukocyte antigen (HLA)-class I-restricted peptide antigenicity by using HSP90 and ORP150 molecular chaperones that act as endogenous Toll-like receptor ligands. In addition to the aforementioned manipulation of the positive loop of tumor immunity, it is necessary to regulate and intervene in the negative loop. In particular, the potential of the expression of HLA class I molecule regulation by epigenetic mechanisms will be discussed. Finally, the type of basic and clinical tumor immunology research highly required currently, and in the very near future, are described.

HLA antigen changes in malignant cells: epigenetic mechanisms and biologic significance

Changes in classical and nonclassical HLA class I as well as HLA class II antigens have been identified in malignant lesions. These changes, which are described in this review are believed to play a major role in the clinical course of the disease since both HLA class I and class II antigens are critical to the interaction between tumor cells and components of both innate and adaptive immune system. Abnormalities in HLA antigen expression in malignant cells, which range in frequency from 0-90%, are caused by distinct mechanisms. They include defects in beta(2)-microglobulin (beta(2)m) synthesis, loss of the gene(s) encoding HLA antigen heavy chain(s), mutations, which inhibit HLA antigen heavy chain transcription or translation, defects in the regulatory mechanisms, which control HLA antigen expression and/or abnormalities in one or more of the antigen processing, machinery (APM) components. More recently, epigenetic events associated with tumor development and progression have been found to underlie changes in HLA antigen, APM component, costimulatory molecule and tumor antigen (TA) expression in malignant cells. The types of epigenetic modifications that may occur in normal and malignant cells as well as their role in changes in HLA antigen expression by malignant cells have been reviewed. The epigenetic events associated with alterations in HLA antigen expression may be clinically relevant as, in some cases, they have been shown to impair the recognition of tumor cells by components of the adaptive immune system. The functional relevance and potential clinical significance of these epigenetic alterations have been addressed. Finally, unlike genetic alterations, epigenetic modifications can, in some cases, be reversed with pharmacologic agents that induce DNA hypomethylation or inhibit histone deacetylation. Therefore, strategies to overcome epigenetic modifications underlying changes in HLA antigen expression in malignant cells have been discussed.

Regulation of MHC class II gene expression by the class II transactivator

MHC class II molecules are pivotal for the adaptive immune system, because they guide the development and activation of CD4+ T helper cells. Fulfilling these functions requires that the genes encoding MHC class II molecules are transcribed according to a strict cell-type-specific and quantitatively modulated pattern. This complex gene-expression profile is controlled almost exclusively by a single master regulatory factor, which is known as the class II transactivator. As we discuss here, differential activation of the three independent promoters that drive expression of the gene encoding the class II transactivator ultimately determines the exquisitely regulated pattern of MHC class II gene expression.

Chaperoning antigen presentation by MHC class II molecules and their role in oncogenesis

Tumor vaccine development aimed at stimulating the cellular immune response focuses mainly on MHC class I molecules. This is not surprising since most tumors do not express MHC class II or CD1 molecules. Nevertheless, the most successful targets for cancer immunotherapy, leukemia and melanoma, often do express MHC class II molecules, which leaves no obvious reason to ignore MHC class II molecules as a mediator in anticancer immune therapy. We review the current state of knowledge on the process of MHC class II-restricted antigen presentation and subsequently discuss the consequences of MHC class II expression on tumor surveillance and the induction of an efficient MHC class II mediated antitumor response in vivo and after vaccination.

Epigenetic inactivation of class II transactivator (CIITA) is associated with the absence of interferon-gamma-induced HLA-DR expression in colorectal and gastric cancer cells

Tightly regulated at the level of transcription, expression of MHC class II molecules varies significantly among gastrointestinal cancers. High levels of MHC class II expression are often associated with a better prognosis, which is indicative of the involvement of CD4+ lymphocytes in tumor suppression, but the molecular mechanism by which MHC class II expression is regulated remains unclear. In the present study, we investigated the expression of one inducible MHC class II molecule, HLA-DR, and its coactivators in a panel of colorectal and gastric cancer cell lines. Interferon-gamma induced expression of HLA-DR in 14 of 20 cell lines tested; the remaining six cell lines did not express HLA-DR. Analysis of the expression of transcription factors and coactivators associated with HLA-DR revealed that the loss of CIITA expression was closely associated with the absence of HLA-DR induction. Moreover, DNA methylation of the 5' CpG island of CIITA-PIV was detected in all cancer cells that lacked CIITA. The methylation and resultant silencing of CIITA-PIV depended on the activities of two DNA methyltransferases, DNMT1 and DNMT3B, and their genetic inactivation restored CIITA-PIV expression. It thus appears that CIITA methylation is a key mechanism that enables some gastrointestinal cancer cells to escape immune surveillance.

MHC class II expression is differentially regulated in plasmacytoid and conventional dendritic cells

Major histocompatibility complex (MHC) class II-restricted antigen presentation is essential for the function of dendritic cells (DCs). We show here that plasmacytoid DCs (pDCs) differ from all other DC subsets with respect to expression of CIITA, the 'master regulator' of MHC class II genes. The gene encoding CIITA is controlled by three cell type-specific promoters: pI, pIII and pIV. With gene targeting in mice, we demonstrate that pDCs rely strictly on the B cell promoter pIII, whereas macrophages and all other DCs depend on pI. The molecular mechanisms driving MHC class II expression in pDCs are thus akin to those operating in lymphoid rather than myeloid cells.